Keep Debian default IMA config

[5kt]

What this PR does / why we need it:
After some internal discussions we decided to keep the IMA configs same as Debian upstream.
The current IMA configuration is hindering us from using the Nvidia gpu operator as the firmware is unable to be loaded because it is not signed - problematic option is CONFIG_IMA_APPRAISE_REQUIRE_FIRMWARE_SIGS

The default config for IMA used upstream is already in the main config.

CONFIG_IMA=y
CONFIG_IMA_SIG_TEMPLATE=y
# CONFIG_IMA_DEFAULT_HASH_SHA1 is not set
CONFIG_IMA_DEFAULT_HASH_SHA256=y
# CONFIG_IMA_DEFAULT_HASH_SHA512 is not set
# CONFIG_IMA_DEFAULT_HASH_WP512 is not set
# CONFIG_IMA_WRITE_POLICY is not set
# CONFIG_IMA_READ_POLICY is not set
CONFIG_IMA_APPRAISE=y
CONFIG_IMA_ARCH_POLICY=y

Which issue(s) this PR fixes:
Fixes #

[Akendo]

LGTM